This invention relates generally to intraocular lenses designed for surgical implantation into the eye as a replacement for a removed natural lens. More specifically, this invention relates to an improved intraocular lens having a preferred unitary or one-piece construction and a related production method, wherein the one-piece lens includes resilient support haptics having improved structural properties.
Intraocular lenses in general are well known for implantation into the eye as a replacement for a natural crystalline lens which has been removed surgically due to a cataract condition, injury, or the like. Such intraocular lenses are typically constructed from a selected transparent and relatively inert plastic material, such as polymethylmethacrylate, to form a lens body of generally disk-shaped configuration with optical characteristics approximately a natural lens. Support structures known commonly as haptics project outwardly from the lens body for contacting adjacent tissue structures within the eye, for purposes of maintaining the lens body in generally aligned relation with the iris and pupil. In some intraocular lens styles, the lens body and related haptics are designed for implantation into the so-called anterior chamber of the eye in front of the iris and pupil, whereas other common lens designs are intended for implantation into the so-called posterior chamber behind the iris and pupil.
Significant design activity has focused upon the haptic support structures in an effort to provide improved biocompatibility within the eye, in combination with sufficient structural strength for reliable support of the lens body while avoiding discomfort attributable to irritation of delicate eye tissues. In this regard, for substantially optimized biocompatibility when implanted into humans, it is generally desirable to form the haptic structures from the same inert plastic material used to form the transparent lens body. The prior art thus includes many examples of unitary or one-piece intraocular lenses having haptic structures of many different specific geometries which are formed by casting or machining to be integral with a lens body. See, for example, U.S. Pat. Nos. 4,687,485; 4,190,049; and 4,134,161. However, these integrally formed haptics have generally required relatively complex and costly manufacturing operations. Moreover, these integral haptics generally do not exhibit sufficient resiliency to avoid undesirable tissue irritation, since manufacturing limitations normally require such one-piece haptics to have relatively large cross-sectional dimensions to provide satisfactory tensile strength.
Alternative haptic support structures have been fashioned from filamentary material such as polypropylene or the like for separate mounted attachment onto a lens body. Such filament haptics typically have an inboard end adapted for physical anchoring within a small counterbored seat formed in the periphery of a lens body, in combination with an outboard support loop having an outwardly convex curvature for contacting eye tissue. While filamentary material beneficially possesses improved resiliency without significantly compromising structural integrity, the formation and assembly of filament haptics to lens bodies involves additional and relatively tedious manufacturing steps. In addition, the resultant intraocular lens includes multiple materials and thus is not preferred by many surgeons.
There exists, therefore, a significant need for further improvements to intraocular lenses, particularly with respect to providing a lens having integrally formed haptic support structures possessing relatively high resiliency together with high structural strength. The present invention fulfills these needs and provides further related advantages.